1. Field of the Invention
The present invention relates generally to apparatus and methods for changing speed and torque from a prime mover. More particularly, the invention pertains to apparatus and method for selecting infinite speed and torque variations for vehicles, wind turbines and industrial speed changers through selected use of a variable throw cam designed to smoothly produce selected, ripple-free speeds and torques.
2. Statement of the Art
Numerous systems and methods have been proposed to change the speed and torque from a prime mover. The present invention relates generally to that class of variable and fixed speed transmissions described as ratchet drives and more particularly to the control mechanisms employed with such drives. Transmissions of this type, known previously, include variable throw eccentrics, variably displaced fulcrums and/or variable length lever arms adapted to produce speed variations. Such systems are shown, for example, in U.S. Pat. No. 3,803,931; U.S. Pat. No. 3,517,913; U.S. Pat. No. 3,229,549; U.S. Pat. No. 3,073,173; U.S. Pat. No. 2,199,052; U.S. Pat. No. 2,159,739; U.S. Pat. No. 3,915,129; Italian Patent No. 460047 and French Patent No. 590,087.
Some of these known systems utilize planetary arrays of one-way clutches while others utilize in-line arrays. Various means of selecting the input-output ratios of the systems have been proposed.
Another known transmission is shown in U.S. Pat. No. 4,116,083. This transmission reverts the power train so that the common shaft is an input shaft instead of an output or stator shaft. In this transmission, the housing operates as the output member.
U.S. Pat. No. 1,770,132 (Van Soden-Fraunhofen) discloses a gear system having cam followers positioned to ride atop a cam turned by an input shaft. A lateral movement of the input shaft displaces the followers on the cam to change the drive ratio between input and output shafts.
U.S. Pat. No. 1,954,767 (Foster) discloses a variable speed transmission wherein a cam is moved to change speed ratio and wherein followers ride on the cams.
U.S. Pat. No. 2,554,463 (Klamp) discloses a variable speed transmission having a plurality of cam followers arranged in a substantially circular spacing about a cam. Klamp suggests positioning the cam followers such that alternate followers are simultaneously rotated in a common direction during the same time period that the remaining cam followers are rotated in an opposite direction. This interrelationship facilitates the connection of adjacent pairs of cam followers by tension springs which act as a means of retaining the cam followers in contact with the cam.
U.S. Pat. No. 2,983,154 (Neukirch) suggests a variable speed mechanical transmission having a plurality of cam followers spacedly positioned about a centrally positioned cam. Neukirch discloses housing-mounted springs which abut against the cam followers and urge them into engagement against the cam. In one embodiment (FIG. 10), Neukirch suggests the placement of a roller on the cam follower.
U.S. Pat. No. 3,803,931 (Bianchini et al.) discloses a variable speed transmission having two sets of cam followers positioned in a substantially circular, spaced orientation about a central cam. A set of cam followers is shown positioned on each of the opposing sides of the disc-like cam.
U.S. Pat. No. 4,487,085 (Collins) discloses an infinitely variable transmission wherein a cam follower includes a rotatably mounted roller which is mounted within a yoke formed within the cam follower.
In applicant's co-pending U.S. Pat. application, Ser. No. 753,044, filed July 2, 1985, applicant has disclosed an Infinite Speed Variation, Constant Power, Ripple-Free Transmission. The disclosed transmission uses a multi-lobed cam, rotatably mounted on a shaft. Followers, positioned to engage the cams, transmit the rotation of the cams to another shaft through use of one-way clutches.
While the gearing systems and transmissions described in the foregoing devices have proven desirable for use, it has been found that such devices do not always permit easy, smooth shifting to allow for effective selection of the infinite gear ratios available with the devices.